Edward A. Romana wrote:
> ~~~
>
> Ok, flowing your advice, I compared the execution time of 2 Maxima and Fortran nested
> do-nothing loops compiled with mode_declare([j,k], fixnum) and implicit none respectively.
> Also I increased the number of loops to overcome process startup time overheads.
> And in the Fortran pgm I added a simple integer counter m=m+1 instruction to to overcome
> the Fortran compiler optimization of the do-nothing loops to zero executed instructions.
>
> The result is that Maxima do-nothing loops compiled using mode_declare are 20 times
> faster than Maxima compilation without it. However Fortran is still 196 times faster
> than Maxima compiled with mode_declare([j,k], fixnum) indexes .
>
> If I understand your explanation, in Maxima even with the loop index declared fixnum,
> the Maxima index variable remains symbolic that is a symbolic integer expression in the
> body of the for-loop can redefine the index. This does not seem too useful me,
> but I am willing to be convinced otherwise, namely are there algorithm examples
> where the expensive symbolic for-loop index is necessary or useful?
>
>
> Ed
>
>
>
I tried your original code with maxima, intel fortran, and gfortran on
my linux box running Fedora core 6. The fortrans are faster but at most
an order of 30, not 196.
If you want me to try your newer code, just send it to me in private email.
Here are the maxima results.
(%i9) showtime: true;
Evaluation took 0.0000 seconds (0.0000 elapsed)
(%o9) true
(%i10) build_info();
Maxima version: 5.15.0
Maxima build date: 8:19 5/2/2008
host type: i686-pc-linux-gnu
lisp-implementation-type: GNU Common Lisp (GCL)
lisp-implementation-version: GCL 2.6.7
Evaluation took 0.0000 seconds (0.0000 elapsed)
(%o10)
(%i11) dispfun(f);
(%t11) f(n):=for j thru 1000 do (for k thru 1000 do return)
Evaluation took 0.0000 seconds (0.0000 elapsed)
(%o11) [%t11]
(%i12) f(1000);
Evaluation took 3.7700 seconds (20.4400 elapsed)
(%o12) done
(%i13) compile(f);
Warning-> return is an undefined global variable.
Compiling gazonk0.lsp.
End of Pass 1.
End of Pass 2.
OPTIMIZE levels: Safety=2, Space=3, Speed=3
Finished compiling gazonk0.lsp.
Evaluation took 0.0000 seconds (0.5000 elapsed)
(%o13) [f]
(%i14) f(1000);
Evaluation took 0.0700 seconds (0.0700 elapsed)
(%o14) done
(%i15) f(1000);
Evaluation took 0.0600 seconds (0.1100 elapsed)
(%o15) done
One fortran result:
[sen at gumbie Speed_test]$ more nest_do.f
program test
do j=1,1000
do k=1,1000
end do
end do
end program test
sen at gumbie Speed_test]$ ifort -O2 nest_do.f -o nest_if_O2
[sen at gumbie Speed_test]$ time nest_if_O2
real 0m0.004s
user 0m0.000s
sys 0m0.000s
[sen at gumbie Speed_test]$ time nest_if_O2
real 0m0.002s
user 0m0.000s
sys 0m0.002s